Double-pass pumping KTA OPO based on unstable resonator with Gaussian reflectivity mirror

A novel double-pass pumping optical parametric oscillator (OPO) with unstable resonator based on Gaussian reflectivity mirror (GRM) was proposed and demonstrated. The output characteristics of double-pass pumping OPO based on non-critical phase matching (NCPM) KTiOAsO4 (KTA) crystal were researched at a pulse repetition frequency of 100 Hz. Compared with the single-pass pumping OPO, the output energy and the conversion efficiency of double-pass pumping OPO were improved by 36 %. The beam qualities of signal and idler were measured and compared with different pump structures, and the results show that beam quality of signal for double-pass pumping OPO barely deteriorated. In addition, the pulse widths of signal and idler under two pumping structures and their variation trends with different pump energies were researched and compared.